Memory is frequently packaged on modules that contain several similar (or identical) integrated circuits (or, for ease of reference, chips), such as dynamic random access memory (DRAM) devices. The memory module may include conductive traces laminated onto a non-conductive substrate (e.g., a printed circuit board or, simply a PCB). Examples of memory modules include dual inline memory modules (DIMMs) and small outline DIMMs (SO-DIMMs).
The temperature of a semiconductor memory (e.g., DRAM) is largely determined by its activity level (e.g., the rate of reads and writes into the memory cells). If the temperature of the memory is too high, then the data stored in the memory may be corrupted or lost. In addition, the memory may be damaged by excessively high temperatures. The temperature of each memory device on a memory module may be different depending on factors such as its level of use, available cooling, and its own unique characteristics. The thermal constraints of memory devices may limit the maximum data access rates that memory device interfaces can support.
Conventional approaches to addressing the thermal constraints of a memory system typically include an external thermal sensor. That is, they typically include a thermal sensor that is affixed to the external portions of a memory module. For example, the thermal sensor may be affixed to one side of a PCB (e.g., to one side of a DIMM or an SO-SIMM). This thermal sensor detects the temperature of the PCB and attempts to infer an approximate temperature of the memory devices based on the temperature of the PCB. The remote thermal sensor may have the capability to trigger an event when a preprogrammed thermal threshold is reached.
There are a number of limitations to the conventional approach of addressing thermal constraints in a memory system. Memory modules are frequently coplanar with the main system board. This means that one face of the memory module is facing the main system board and another face of the module is facing away from the board. Each side of the memory module is likely to have a different temperature and a single thermal sensor affixed to one side of the module will be unlikely to infer an accurate temperature for the opposing side of the module.